In Unified CM 15 EMCC, Login is unavailable(28) (Untrusted IP Error) occurs when Validate IP Address is enabled and the requesting IP address is not in the trusted list.
Checked 2026-10-02
- Vendor
- Cisco
- Product
- Cisco Unified Communications Manager
- Subsystem
- Extension Mobility Cross Cluster
- Deployment
- on-premises
- Region
- not restricted
- Release range
- 15 and SUs
- Checked
- 2026-10-02
Sources
- Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Extension Mobility Cross Cluster — Cisco Systems · tier 2 current vendor documentation · Troubleshooting Extension Mobility Cross Cluster > service error codes, row 28
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting Extension Mobility login failures in Unified CM: source note cucm-extension-mobility-troubleshooting-emcc-err-28-untrusted. WarmTransfer. https://warmtransfer.net/knowledge/claims/cucm-extension-mobility-troubleshooting-emcc-err-28-untrusted
BibTeX
@misc{warmtransfer-claim-cucm-extension-mobility-troubleshooting-emcc-err-28-untrusted,
title = {Troubleshooting Extension Mobility login failures in Unified CM: source note cucm-extension-mobility-troubleshooting-emcc-err-28-untrusted},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/cucm-extension-mobility-troubleshooting-emcc-err-28-untrusted},
note = {Source note cucm-extension-mobility-troubleshooting-emcc-err-28-untrusted, checked 2026-10-02}
}